S. Tez
Radiology Clinic
19 Mayıs Hospital
Dikmen, Ankara, Turkey

M. Tez
Surgery Clinic
Ankara Numune Training and Research Hospital
Sıhhiye, Ankara, Turkey

We have read the article entitled “Treatment of Benign Thyroid Nodules: Comparison of Surgery with Radiofrequency Ablation” with great interest and congratulate the authors.¹

Since Dupuy et al² published the application of radiofrequency ablation to treat recurrent thyroid cancers, radiofrequency ablation has been widely used for the treatment of benign thyroid goiters. However, there are some issues that must be clarified in the present article.

1. What are the pathology results of the thyroidectomy group? Is there a malignant pathology report?

   Incidental papillary carcinoma (IPC) of the thyroid has been accepted widely as a tumor measuring ≤1 cm. A 10% incidence of patients with IPC with multinodular goiter with benign cytology was reported in the study of Bradly et al.³ Although IPC progression is infrequent, a few cases of local spread or nodal metastases are reported in the long-term, and most patients can be effectively treated with lobectomy or thyroidectomy.⁴

2. What is the number of total thyroidectomy and lobectomy procedures? Are surgical complications different in these groups?

   Unilateral thyroidectomy (lobectomy) may be preferred to retain some function of the thyroid, allowing patients to avoid life-long hormone replacement therapy. The complication rate after total thyroidectomy has been reported to be between 5% and 33%. On the other hand, postoperative complications after lobectomy are reported between 2% and 3%.⁵ Complications of radiofrequency ablation, total thyroidectomy, and lobectomy could be presented separately.

3. The authors stated, “Comparison of the two groups was done by the Wilcoxon signed rank test” in the “Statistical Methods” section.¹

The Wilcoxon signed rank test is a nonparametric statistical hypothesis test used when comparing 2 related samples, matched samples, or repeated measurements on a single sample to assess whether their population mean ranks differ. Because the surgery and radiofrequency ablation groups are not related, the Wilcoxon signed rank is not a suitable method for statistics.

References

1. Che Y, Jin S, Shi C, et al. Treatment of benign thyroid nodules: comparison of surgery with radiofrequency ablation. AJNR Am J Neuroradiol 2015 Mar 26. [Epub ahead of print] » Abstract/FREE Full Text
2. Dupuy DE, Monchik JM, Decrea C, et al. Radiofrequency ablation of regional recurrence from well-differentiated thyroid malignancy. Surgery 2001;130:971–77 » CrossRef » Medline
3. Bradly DP, Reddy V, Prinz RA, et al. Incidental papillary carcinoma in patients treated surgically for benign thyroid diseases. Surgery 2009;146:1099–104 » CrossRef » Medline
4. Papini E, Guglielmi R, Gharib H, et al. Ultrasound-guided laser ablation of incidental papillary thyroid microcarcinoma: a potential therapeutic approach in patients at surgical risk. Thyroid 2011;21:917–20 » CrossRef » Medline
5. Bauer PS, Murray S, Clark N, et al. Unilateral thyroidectomy for the treatment of benign multinodular goiter. J Surg Res 2013;184:514–18 » CrossRef » Medline

Reply

J.H. Baek
Department of Radiology and Research Institute of Radiology
University of Ulsan College of Medicine
Asan Medical Center
Seoul, Korea

We have read the letter regarding our recently published article in the American Journal of Neuroradiology¹ and hereby provide a reply. Tez and Tez suggested the issue of incidental small papillary thyroid cancer. A 10% incidence of incidental small papillary thyroid cancer was found in multinodular goiter with benign cytology. To minimize missing cancer, the Korean Society of Thyroid Radiology (KSThR) recommended at least 2 different benign biopsy results before radiofrequency ablation.² In addition, the KSThR recommended careful examination of sonography findings and lymph node metastasis before treatment.³ KSThR also does not recommend thyroid radiofrequency ablation for follicular neoplasms or primary thyroid cancers.² On the basis of these KSThR recommendations, missing cancer was a rare complication after radiofrequency ablation in a large-population multicenter study⁴ and long-term follow-up studies by thermal ablation techniques.^5⇓⇓–8

Regarding complications after surgery and radiofrequency ablation, surgery showed a higher incidence of hypothyroidism than radiofrequency ablation (71% versus 0%) in our study. Because our study included a considerable number of patients with total thyroidectomy (due to bilateral thyroid nodules), hypothyroidism was an inevitable complication in these patients. Hypothyroidism depends on the surgical methods (ie, total thyroidectomy or lobectomy). Regarding the statistical issue, the Wilcoxon signed rank test was used for comparison of the volume reductions between enrollment and the follow-up visit of the radiofrequency group.

The main conclusion of our study was that radiofrequency ablation effectively treats benign thyroid nodules with a low amount of complications.¹ Hence, radiofrequency ablation may be considered as possibly the first-line treatment for benign thyroid nodules. However radiofrequency ablation has a potential limitation of missing incidental small papillary thyroid cancers. This limitation should be carefully validated in the future.

References

1. Che Y, Jin S, Shi C, et al. Treatment of benign thyroid nodules: comparison of surgery with radiofrequency ablation. AJNR Am J Neuroradiol 2015 Mar 26. [Epub ahead of print] » Abstract/FREE Full Text
2. Na DG, Lee JH, Jung SL, et al; Korean Society of Thyroid Radiology (KSThR), Korean Society of Radiology. Radiofrequency ablation of benign thyroid nodules and recurrent thyroid cancers: consensus statement and recommendations. Korean J Radiol 2012;13:117–25 » CrossRef » Medline
3. Lee YH, Baek JH, Jung SL, et al. Korean Society of Thyroid Radiology (KSThR), Korean Society of Radiology. Ultrasound-guided fine needle aspiration of thyroid nodules: a consensus statement by the Korean Society of Thyroid Radiology. Korean J Radiol 2015;16:391–401 » CrossRef » Medline
4. Baek JH, Lee JH, Sung JY, et al. Korean Society of Thyroid Radiology. Complications encountered in the treatment of benign thyroid nodules with US-guided radiofrequency ablation: a multicenter study. Radiology 2012;262:335–42 » CrossRef » Medline
5. Lim HK, Lee JH, Ha EJ, et al. Radiofrequency ablation of benign non-functioning thyroid nodules: 4-year follow-up results for 111 patients. Eur Radiol 2013;23:1044–49 » CrossRef » Medline
6. Spiezia S, Garberoglio R, Milone F, et al. Thyroid nodules and related symptoms are stably controlled two years after radiofrequency thermal ablation. Thyroid 2009;19:219–25 » CrossRef » Medline
7. Døssing H, Bennedbæk FN, Hegedüs L. Long-term outcome following interstitial laser photocoagulation of benign cold thyroid nodules. Eur J Endocrinol 2011;165:123–28 » Abstract/FREE Full Text
8. Valcavi R, Riganti F, Bertani A, et al. Percutaneous laser ablation of cold benign thyroid nodules: a 3-year follow-up study in 122 patients. Thyroid 2010;20:1253–61 » CrossRef » Medline